Electrode for electrolytic conductivity cells



Feb."3, 1925. 1,524,937

" E.A.KEELER ELECTRODE FOR ELECTROLYTIC CONDUCTIVITY CELLS Filed Jan.10. 1924 .INVENTOR: far! A, /feeler,

ATTORNEY Patented Feb. 3, 13925,

I isaaaai pairs stares Pars-Ni orrica EARL A. KEELER,-OF OAK LANE,PENNSYLVANIA, ASSIGNOR TO'THE BROWN INSTBU- PHILADELPHIA, PENNSYLVANIA,A CORPORATION OF PEN-N1 mnn'r COMPANY, SYLVANIA.

ELECTRODE non ELECTROLYTIC (EONDUCTIVITY cams.

Applicationtled January 10,1924; serial No. 685,366.

To all whom it may concern." j

Be it known that I, EARL A. KEELER, a' citizen of the United States, anda resident of Oak Lane, county of Philadelphi ag State 5 ofPennsylvania, have invented certainnew and useful Im rovement's inElectrodes for Electrolytic onductivity Cells, of which the following isa specification.

The present invention relates to electroto lytic conductivitycells,'-and more particularly to improvements in the electrodes used inconjunction with such cells.

Electrolytic conductivity cells are used to measurethe conductivity ofchemical solu-l.

1e tions, to determine the amount of salt, al-

, kali or acid in the solution, and in carrying out this measurement thetwo electrodes of the cell are immersed in the solution and theresistance to current flow determined by meansof a Wheatstone bridgecircuit, which is the more general method of making such determination.The resistance of the electrolytic conductivity cell constitutes one armof the bridge. In measuring the conductiv- 2 ity of chemical solutionsby this method a serious difiiculty arises in that this passage ofcurrent between the electrodes, results in the evolution of a gas, whichdeposits as a thin film upon. the electrode, and produces 0 an eflectknown as polarization, and while this deposit is practically invisibleit creates sufficient increase in the resistance offered to current flowas to introduce an error into the reading of the conductivity-of the.solu% tion. In other words, this thin film of gas produces an increaseof resistance which indicates an apparent. change in electrolyticconductivity of the solution, and therefore indicates an apparent changein the amount 40 I of dissolved materials.

. Various 'meanshave been triedfor minimizing the errors ofpolarization, one of which is to increase the area of the electrodes sothat the current density is reduced and the evolution of gas distributedover a greater area, but this is impractical because of the spacerequired. The more widely used means for reducing the errors due topolajization consists in employing blectrod s 60 which are made of anoble metal, such as platinum, gold or palladium, but even this meanshas disadvantages, namely, a prohibitive cost if the electrodes are madelarge enough to fiilfil the requirements oi operation, and if made, asthey generally are, relatively small and delicate, they become brokenand require constant repairing. The

' noble metals are used .bboause platinum black or other depolarizingUrea-11s can be readily deposited upon theexposed surfiace.

It is an object of the present invention to retain all the advantagesaccompanying the use otno'bl'emetal electrodes but tosecure theruggedness and strength necessary to meet the severe requirements ofcommercial use. It is also an object of the invention to provide animprovedoelectrodefor electroy lo conductivity cells which not onlyoperates in an improved manner but can be manufactu'red and maintainedat a relatively low cost.

In the accompanying drawings, Fig. 1 represents a section of' anelectrode embodying oneform of the present invention; Fig. 2

represents a side. elevation in part section of one form of anelectrolytic conductivity cell employing l electrode of the presentinvention; Fi .3 r resents a diagram of a circuit by which theconductivity ofkthe solution is measured with a cell embodying. thepresent invention; and Fig. 4 represents an electrolytic conductivitycell embodyinganother form of the invention partly broken away to showthe tlI'OdSL I f I 'Referring to the drawings, one form of the presentinvention comprises an electrode or terminal 10, which is mounted on abase arrangement of the elec- 11 of porcelain or other suitableinsulating material through which a lead wire of the electrode can beconveyed to the electric circuit without making contact or otherwiseshort qircuiting the other lead of the cell.

For the purpose of providing an electrode of substantial and ruggedform, but one tages of the delicate and expensive electrodes '95 whichretains all the efliciency and advanmanufactured from a noble metal,such as platinum, gold or palladium, the present electrode 10 is formedof a base metal body strength and ruggedness sothat the electrode willstand jlip under hard usage and 'be unaffected by the necessary frequent12, ofsuch size and configuration as to give prises a tubular member 18,which has able plating process a coating 13 of platinum, though this isonly by Way of example, and it will be understood that the coating sodeposited may be of any other suitable noble metal, the result beingthat the base metal has its surface transformed from one subject tocorrosion and unsuited to electroplating and deposition (it-depolarizingfilm to one resisting corrosion and suited to the deposition of adepolarizing film.

As a means for minimizing the effect known as polarization, namely, theformation of a thin film of gas over the surfa e of the electrode, thebody 12, with its coating 13 of platinum or other suitable metal, issubjected to a further electroplating operation in asolution ofapproximately 3. per cent platinum'chloride in order to Form a film 14over the surface of .the platinum coating 13, which is known as platinumblack, or, in the case of palladium, as palladium black, which film hasthe property of increasing the surface area of the platinum electrodeand of absorbing the gases which are given off when cin'rent passes fromone electrode to the other through the solution.

Thus, the complete electrode or terminal is made u of a substantial bodypart comosed o a base metal and upon which there 1s first anelectroplated coating of a noble metal and last an absorbent 'de osit orfilm, such, for example, as platinum iilack.

In Fig. 2, an electrode 10, constructed and described -in connectionwith Fig. 1, is shown, mounted axially on a porcelain insulator 15 andin electrical connection with a binding post 16, to which one wire 17 ofthe electric circuit is arranged to be connected. In this form of cellthe second electrode or terminal of the circuit comthreaded connectionwith the reduced neck of a metal plug 20, which has its body portionexteriorly threaded as shown at 21 for the purpose of connecting thecell to a pipe or other receptacle in'which the liquid under test isplaced. This plug 21 is provided.

with a suitable hexagon surface 22, whereby it can be gripped with awrench for; tightening in place, and also has a stuffing box structure23 to prevent leakage of the liquid outwardly through the cell. At anysuitable location in the metal body of the plug 21, connection may bemade for a return wire 24 of the circuit. which includes the conductor17. In order to bring-the solution under test in the proper relationwiththe electrodes 10 and 18,-the electrode 18 is provided with suitableperforations 25 which permit the liquid or solution to circulate freelywithin the electrode '18 and about the electrode 10. The cell of thecharacter shown in Fig. 2 in operation is located in one arm ofaWheatstone bridgecircuit,

as shown at 26, the other arms of which have resistances 27, 28 and 29of values sista-nce is made bya galvanomcter 30 in the usual manner. Thecurrent from a source 31 is supplied by conductors 32 and 33 to thebridge, thus,"completingthe circuit by which current passes through thecell 26 and by the resistance of this solution in whi h the cell isimmersed its conductivity can be determined from a reading of thegalvanomcter;

In Fig. 1 another form of the invention is shown in which athreaded plug33 forms a casing enclosing two electrodes 3-1 and 35. each oftheconstruction as described in conjunction with the electrode 10, andthe two together torming terminals of the same circuit, which aremounted in spaced relation '\\'ithin a perforated tube 36 through whichthe test solution .has free circulation. Electrodes 34 and areresp'ectivelyconnccted byconducting leads 37 and 38 to the circuit inwhich the cell is located. In use, the conductivity cell embodying anelectrode or electrodes of the present invention is adapted-to bemounted in a pipe line through which a solution under test iscirculating, or it may be located in any suitable container in which islocated a solution the conductivity ofwhich is to be determined. Theinvention may be embodied,

described my invention, I

electric circuit and arranged tobe sub merged in a solution under test,one of said electrodes being formed of a base metal body plated with anoble metal and having a depolarizing film deposited thereon, and a bodymounting said electrodes in insulated spaced relation,

'2; In an electrolytic conductivity cell, a

pair'of electrodes forming terminals of an electric circuit and arrangedto be submerged-in a solut on under test, one of said electrodes beingformed of a base metal body'plated" with platinum and having a platinumblack film deposited thereon, and a body mounting said electrodes ininsulated spaced relat icn.

3. An electrolytic conductivity cell comv prising a tubular'base metalelectrode, a second electrode within saidtubular electrode comprising abase metal body plated with a noble metal and having a depolarizing filmdeposited thereon, 'a base mounting said electrodes in insulated spacedrelation, and conducting wires, respectively connecting said electrodesto an electrical measuring circuit. I

4. An electrolytic conductivity cell comprising a tubular base metalelectrode, a second electrode within said tubular electrode comprising abase metal body plated. with platinum and having a platinum black filmdeposited thereon, a base mounting said electrodes in insulated spacedrelation, and conducting wires respectively connecting said electrodesto an electrical measuring circuit.

5. An electrolytic conductivity cell comprising a tubular perforatedbase metal electrode, a second electrode within said tubular electrodecomprising a base metal body plated with platinum and having a platinumblack film deposited thereon, a base mounting said electrodes ininsulated spaced relation, and conducting wires respectively connectingsaid electrodes to an electrical measuring circuit.

6. As a new article of manufacture, an electrode for electrolyticconductivity cells comprising a rugged base metal body with a noblemetal electroplated thereon and a depolarizing film deposited on saidnoble metal. I I

7. The method of forming a rugged, substantial electrode for electrol icconductivity cells which consists of e ectroplating a noble metalcoating upon a relatively large base metal body and then depositing adepolarizing film upon said plated metal coat- 1n igned at Philadelphia,in the county of Philadelphia, and State of Pennsylvania, this 29th dayof December, 1923.

EARL A. KEELER,

